The question “How much water do I have in my tank?” is one that many rainwater catchment system owners often ask themselves. Not knowing the answer to this basic question can result in not getting the most out of one’s water catchment system. At worst, it can result in running a pump dry, which can ruin an expensive system component.

Fortunately, today there are many, many options for determining the depth of water in the tank and it is highly recommended that some type be installed when installing a system. Many options can installed after the fact, but may be more expensive due to the need to install additional wires and piping.

There are depth gauges for above below ground tanks, ranging in price from less than one hundred dollars to several hundreds of dollars. Below is a quick sample of just a few that are available, many on the Internet.

The Rain Alert Tank Level Monitor is an inexpensive unit that can be used in either a above or a below ground tank. It uses ultrasonic technology inside the tank and RF wireless to the base unit, this monitoring system tells you how much rainwater is in your tank or cistern.

It is typically available for less than $100 and shows the depth of the water in the tank through bars on the display.

The unit should be within about 50 feet of the base unit which is installed in the tank or on top of the tank. I recommend this unit only in above ground tanks due to the difficulty in getting it correctly attached in below ground tanks.

Another options is the RainHarvesting Tank Gauge™. It is a water level indicator that is simple and easy to install. It is suitable for above ground, vented tanks up to 100" in height. The gauge is easy to install and uses no battery.

It features an easy-to-read display dial and utilizes a weight float, suspended on a string line to provide accurate readings. The string is attached to a weight float. As the water level goes up and down in the tank, the gauge changes position. There are several others on the market like this gauge.

Another simple and inexpensive depth gauge is the pneumatic-style level gauge. Instead of using a string and a float, it uses pressure to translate water depth to the display. The product is easy to install in either above or a below ground tank and can be readily installed in cisterns with limited access. It is highly pressure-sensitive and indicates water depth in inches, not feet, so it is very accurate.

Moving to the more expensive options which are geared towards below ground tanks, you have wired and wireless options.

These devices typically use what is called a transducer and require either batteries or access to electricity. Pressure transducer sense the depth of the water in the tank through pressure and then relay this pressure reading to a display unit. It is highly recommended if you are going to use one of these devices and it has the ability to be plugged in to a power transformer, buy the transformer. Otherwise, you will be constantly changing batteries and this is bad for many reasons

Another option is Conservation Technology’s digital water level gauge. It is an electronic device that accurately displays the water level in a rainwater tank from 0 to 100% using a transducer that hangs in the tank. This unit has two pieces, the display and the unit that is mounted in the tank and can be used to measure tanks up to 19 feet deep. As with all the higher-end units this unit requires electricity. Due to the possibility of radio-frequency interference, this device is not recommended for use in steel tanks or tight spaces. This unit is generally around $300

All these devices, from simple to expensive depth gauges require you to translate what a specific depth translates in your specific tank in gallons.

It is also possible to build your own, simple level gauge for your above ground tanks. If you are interested in building your own gauge, find out more here.